The modern fire place was largely devised by Count Rumford at the end of the 18th century. Count Rumford realised that the amount of smoke emitted into a room could be reduced by a reduction in the depth of the throat of the fireplace (from front to back). He also realised that the amount of heat radiated into a room could be increased by angling the side covings at about 45 degrees of arc to the back surface of the fireplace.
Rumford also discovered that if the upper part of the fireplace back wall is inclined forwards instead or being vertical, the heat given out is markedly increased. Modern firebacks as specified in BS 1251:1987 utilise much of the Rumford design having angled side covings with the upper back wall being inclined forwards at about 35 degrees of arc from the vertical starting at a height of about 340 mm (about 13.5 inches) from the base of the fireplace.